Several of the dead are police officers. Putin denounces 'a crime against Russia.'

Double suicide bombings struck the strife-ridden Russian republic of Dagestan on Wednesday morning, killing 12 people and injuring dozens.

The attacks came as violent punctuation to this week's bombings aboard Moscow's subway, which killed 39 and stirred fresh fears that volatility in Russia's mostly Muslim Caucasus region is seeping deep into the rest of the country.

Russian Prime Minister Vladimir V. Putin again lashed out at militants, saying this week's bombings could be linked and calling for reinforcement of police ranks in the north Caucasus.

"I don't rule out that the same terrorists were involved," Putin told a government presidium in Moscow. "It does not matter for us in what part of the country these crimes have been committed, or who -- people of what ethnicity or religion -- have fallen victims to these crimes. "We see this as a crime against Russia."

Wednesday morning's first bombing struck on Lenin Road in Kizlyar, the capital of Dagestan. The driver of a Russian-made off-road vehicle ignored the commands of a police patrol to pull over, the interior minister said. As the police veered closer to the car, the suicide bomber blew up the vehicle.

Less than half an hour later, when medical teams and law enforcement had rushed to the scene, a man in a police uniform walked into a group of police standing near an ambulance and blew himself up.

At least seven of the dead were police officers, including the district police chief.

The bombers chose a stretch of road close to the Interior Ministry, Federal Security Services and the FSB, the modern-day successor to the KGB. A school is also nearby.

"It is necessary to find out where the deadly cargo was heading," Russian Interior Minister Rashid Nurgaliyev told reporters. "It is also important to increase vigilance at police departments and executive and legislative government bodies."

The first explosion contained the equivalent of 220 pounds of TNT, investigators said. The massive bomb blasted a crater into the road.

Violence has been grinding along for years in the Caucasus, sometimes drifting from one republic to the next. In the days since the Moscow bombing, gun skirmishes have erupted in Chechnya and insurgents operating from the forest attacked a group of police in Dagestan.

But this week's attacks in Moscow have focused national attention on the country's volatile southern edge once again. The women who blew themselves up on the subway are believed to have traveled to the capital from the Caucasus.

"The explosions on the Moscow metro and today's explosions in Kizlyar are links of the same chain," Dagestani President Magomedsalam Magomedov told reporters. "These people do not need peace. They want war."